Add "Mobile Friendly" in application details

[VaZark]

With the recent surge of interest in linux-based mobile devices and the evolution of responsive support in GUI frameworks, it would be useful to users to be able to see if the application is mobile-friendly.

The value can be updated by the app owners/maintainers and displayed in the Additional Details section. This also incentivises app developers to support the mobile form factor if their apps can be used on mobile.

[BrainBlasted]

Perhaps it could follow a scheme like this: https://adrienplazas.com/blog/2020/10/15/specify-form-factors-in-your-librem-5-apps.html